1. Field of the Invention
The present invention relates to an electronic component and a method of producing the same, and more particularly to a ceramic electronic component having improved external terminal electrodes and a method of producing the same.
2. Description of the Related Art
FIG. 15 is a perspective view showing a conventional ceramic electronic component 1.
The ceramic electronic component 1 defines a capacitor, an inductor, a resonator, a circuit substrate, or other suitable electronic components. The ceramic electronic component 1 includes a member 2 having a laminated or single-layer structure.
The ceramic electronic component member 2 has a rectangular parallelepiped shape which includes first and second main surfaces 3 and 4 disposed opposite to each other and four side surfaces 5, 6, 7, and 8 connecting the first and second main surfaces 3 and 4. A plurality of external terminal electrodes 9 is provided on at least one side surface of the ceramic electronic component member 2, for example, on the side surfaces 5 and 7. These external terminal electrodes 9 are provided on the inner walls 10 of concavities having a semicircular cross-section provided on the side surfaces 5 and 7.
The ceramic electronic component 1 is produced as follows.
First, a ceramic green molded product 11 as shown in FIG. 16 is produced. When the ceramic electronic component member 2 has a laminated structure, a plurality of ceramic green sheets are laminated to produce the ceramic molded product 11. A plurality of the ceramic electronic components 1 are produced from the ceramic green molded product 11.
Next, a plurality of through-holes 12 are formed in the ceramic green molded product 11 as shown in FIG. 16. The positions of the through-holes 12 correspond to positions where the external terminal electrodes 9 are to be formed.
Moreover, as shown in FIG. 16, cutting grooves 15 are formed on one main surface 13 or on both main surfaces 13 and 14 of the ceramic green molded product 11. FIG. 18 clearly shows that the cutting groove 15 is formed on both of the main surfaces 13 and 14. When a plurality of the ceramic electronic components 1 are produced in a later process, the cutting grooves 15 facilitate breaking along the boundary lines between the plurality of the ceramic electronic components. For example, the cutting grooves 15 are formed to have a depth that is equal to about one third to one sixth of the thickness of the ceramic green molded product 11.
Then, the ceramic green molded product 11 is fired, whereby a ceramic sintered product 16 can be obtained. FIG. 17 is a cross-sectional view of a portion of the ceramic sintered product 16.
Subsequently, electrically conductive paste 17 is applied on the inner walls of the through-holes 12, and thereby, the terminal conductors 18 to be formed into the external terminal electrodes 9 are formed on the inner walls of the through-holes 12, respectively, as shown in FIG. 17. To form each terminal conductor 18, for example, screen printing is performed. That is, the ceramic sintered product 16 is placed on a stand 21 having holes 20 to which a vacuum is applied as shown by arrows 19, with the holes 20 and the through-holes 12 being aligned. The electrically conductive paste 17 is applied onto the inner walls of the through-holes 12 by moving a squeegee 23 over a screen 22.
In the above-described screen printing process, the electrically conductive paste 17 is applied to the main surface 13 of the ceramic sintered product 16 in a desired pattern, if necessary, whereby conductor films for wiring are formed.
Succeedingly, the terminal conductors 18 and the conductor wiring films formed with the conductive paste 17 are fired.
If the ceramic green molded product 11 has a laminated structure, the process illustrated in FIG. 17 is carried out for the ceramic green molded product 11 in the green state. In some cases, the conductive paste 17 forming the terminal conductors 18 and the other wiring conductors are fired together with the ceramic green molded product 11.
Next, the surfaces of the terminal conductors 18 are plated with nickel/gold, nickel/tin, nickel/solder, or other suitable conductive material.
Next, components are mounted on the main surface 13 of the ceramic sintered product 16.
The cutting grooves 15 may be formed after the process illustrated FIG. 17, which is carried out before firing, after the plating process, or after the components are mounted.
The ceramic sintered product 16 having the terminal conductors 18 disposed on the inner walls of the through-hole 12 are formed as described above. FIG. 18 shows a portion of the ceramic sintered product 16.
Then, the ceramic sintered product 16 is broken along the cutting grooves 15, and the plurality of the ceramic electronic components 1 are separated. FIG. 19 is a partially enlarged perspective view of a portion of the separated ceramic electronic component 1. FIG. 19 shows a concavity 10 formed by splitting the through-hole 12 and the external terminal electrode 9 formed by splitting the terminal conductor 18.
When the ceramic sintered product 16 is broken as described above, the terminal conductors 18 are split when tensile stress is applied. Therefore, the splitting forms split surfaces 24 which are exposed on the external terminal electrode 9.
The above-described ceramic electronic component 1 and the method of producing the same have the following problems.
The split surfaces 24 formed on the external terminal electrodes 9 oxidize because they are not plated with the plating film. Thus, the soldering properties of the split surfaces 24 are deteriorated. As a result, satisfactory soldering to the external terminal electrodes 9 is not possible.
Moreover, when the ceramic sintered product 16 are broken along the cutting grooves 15, the through-holes 12 are split in such a manner that the terminal conductors 18 on the inner walls of the through-holes 12 are torn off. Thus, the terminal conductors 18 often do not accurately split into halves along the cutting groove 15. In some cases, severe defects are caused. That is, one of the halves is chipped which causes electrical disconnection. Moreover, a fatal deficiency may be caused. That is, the terminal conductors 18 may be partially chipped together with a portion of the ceramic sintered product 16.
To solve the above-described problems, the thickness of each terminal conductor 18 and that of the plating film formed thereon is decreased. However, the decrease of the thickness causes a defect, such as disconnection.
If the external terminal electrodes 9 are formed after the ceramic sintered product 16 is broken along the cutting grooves 15, the above-described problems are solved. However, in this case, the production efficiency is deteriorated.
Moreover, to solve the above-described problem of chipping of the external terminal electrodes 9 caused when the ceramic sintered product 16 is broken along the cutting grooves 15, the terminal conductors 18 must be hollow, as clearly shown in FIG. 17. Therefore, the diameter of the through-hole 12 cannot be significantly reduced. As a result, the size of the ceramic electronic component 1 cannot be significantly reduced.
As shown in FIG. 17, the terminal conductors 18 are formed to be hollow as described above while the peripheries of the holes 21 of the stand 20 are not smeared with the conductive paste 17. Accordingly, the conductive paste 17 must be screen-printed while a vacuum is applied to the holes 20 each having a diameter larger than the through-holes 12. Thus, portions 25 extending onto the main surfaces 13 and 14 are formed for each of the external terminal electrodes 9. However, the presence of the extended portions 25 prevents substantial reduction of the interval at which the external terminal electrodes 9 are arranged. As a result, a substantial reduction in the size of the ceramic electronic component 1 cannot be achieved.
The characteristics of the ceramic electronic components 1 must be measured before the components 1 are shipped. However, before the ceramic sintered product 16 is broken along the cutting grooves 15, the terminal conductors 18 to be formed into the external terminal electrodes 9 of a ceramic electronic component 1 are continuous to those of the adjacent ceramic electronic component 1 in the sintered product 16. Thus, the characteristics of each ceramic electronic component 1 cannot be measured before the ceramic sintered product 16 is broken along the cutting grooves 15. Thus, the measurement of the characteristics cannot be efficiently performed.
If the ceramic electronic component 1 is used as a circuit board, other electronic components may be mounted onto the main surface 3 or 4 of the ceramic electronic component member 2. In this case, the mounting of the electronic components onto the ceramic sintered product 16 is more efficient. However, the characteristics of each of the ceramic electronic components 1 cannot be measured, when the components are present in the form of the assembled electronic component. Thus, the electronic components are mounted on defective ceramic electronic components as well as acceptable ceramic electronic components. This increases the cost of manufacturing the electronic components.
To overcome the above-described problems, preferred embodiments of the present invention provide a greatly improved electronic component and a method of producing the same.
According to a first preferred embodiment of the present invention, an electronic component includes a member having first and second main surfaces opposite to each other, and four side surfaces connecting the first and second main surfaces, at least one of the side-surfaces being provided with a recess portion extending from the first main surface to the second main surface, and a plurality of external terminal electrodes arranged in the recess portion.
The external terminal electrodes are arranged to extend from the first main surface to the second main surface, or may be arranged to extend from the first main surface, but not reaching the second main surface.
Preferably, a plurality of concavities are arranged in the recess portion, and the external terminal electrodes are arranged so as to be filled into the concavities, and the surface of the external terminal electrodes have a common flat surface with the bottom surface of the recess portion.
The member of the electronic component has a laminated structure or a single layer structure. If the member of the electronic component has a laminated structure, the member includes a plurality of ceramic layers laminated together, and an internal conductor film provided on a desired interface between the ceramic layers.
Preferably, an external conductor film is provided on at least one of the first and second main surfaces of the member of the electronic component.
Preferably, the external terminal electrodes each have a portion extending onto at least one of the first and second main surfaces.
The surface of each external terminal electrode is preferably entirely covered with a plating film.
Moreover, another preferred embodiment of the present invention provides a method of producing an electronic component.
According to a second preferred of the present invention, a method of producing an electronic component includes the steps of preparing a ceramic green molded product having a plurality of terminal conductors to be formed into external terminal electrodes and extending in the thickness direction over at least a portion of the thickness thereof, forming a via-hole having an elongated cross section along a line on which the plurality of the terminal conductors of the ceramic green molded product are arranged, the via-hole piercing the ceramic green molded product between the first and second main surfaces thereof opposite to each other, wherein a portion of each of the plurality of the terminal conductors is exposed on the inner surface of the via-hole, firing the ceramic green molded product to obtain a ceramic sintered product, and splitting the ceramic sintered product along a split line passing through the via-hole, wherein the terminal conductors exposed on the inner surface of the via-hole are arranged in a recess portion formed by splitting the via-hole, and the ceramic electronic component is separated from the ceramic green molded product.
In the case in which the electronic component has a laminated structure, preferably, the step of preparing the ceramic green molded product includes laminating ceramic green sheets having a plurality of the terminal conductors provided in the thickness direction thereof so as to pass through the ceramic green molded product.
Moreover, the step of preparing the ceramic green molded product may further include forming conductor films and via-hole conductors for wiring on and in the ceramic green sheets.
According to a third preferred embodiment of the present invention, a method of producing an electronic component includes the steps of preparing a ceramic green molded product, forming a via-hole having an elongated cross section which pierces the ceramic green molded product between the first and second main surfaces opposite to each other, firing the ceramic green molded product to obtain a ceramic sintered product, forming a plurality of external terminal electrodes on the ceramic green molded product or the ceramic sintered product so as to be arranged on the inner surface of the via-hole, and splitting the ceramic sintered molded product along a split line passing through the via-hole, whereby the plurality of the external electrodes formed on the inner wall of the via-hole are arranged in a recess portion formed by splitting the via-hole, and the ceramic electronic component is separated.
In the case in which the electronic component has a laminated structure, the step of preparing the ceramic green molded product includes laminating a plurality of ceramic green sheets.
Preferably, the step of preparing the ceramic green molded product includes forming a conductor film or a via-hole conductor for wiring.
According to the second and third preferred embodiments of the present invention, preferably, the ceramic sintered product is an assembled electronic component from which a plurality of the electronic components are separated, the step of splitting the ceramic sintered product includes splitting the assembled electronic component, and in the step of forming the via-hole, the via-hole is formed so as to split the terminal conductors. Specifically, according to the second preferred embodiment of the present invention, in the step of forming the via-hole, the via-hole is formed so as to split the terminal conductors.
Preferably, the method of producing a ceramic electronic component further includes the step of measuring the characteristics of each of the ceramic electronic components in the state of the assembled electronic component before the step of splitting the assembled electronic component.
Also preferably, the method of producing a ceramic electronic component further includes the step of plating the surfaces of the external terminal electrodes before the step of splitting the ceramic sintered product.
The present invention is also intended for a ceramic electronic component obtained by the above-described method of producing the ceramic electronic component.
Other features, elements, characteristics, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention with reference to the attached drawings.